Method for testing the reliability of an electrochemical gas sensor

ABSTRACT

The present invention is a method by which the deterioration judgement and the correction of an electrochemical carbon monoxide gas sensor are simply carried out without using the correction gas. The method of the present invention is that: the voltage is applied from the outside so that the working electrode of the electrochemical carbon monoxide gas sensor is operated as the negative electrode, and the counter electrode is operated as the positive electrode, and hydrogen is generated from the working electrode, and oxygen is generated from the counter electrode; after that, the potential of the working electrode and the counter electrode is returned to the operation potential as the sensor; and by using the reaction on the hydrogen remained in the vicinity of the working electrode, the sensor current is generated, thereby, it is tested whether the sensor is normally operated.

TECHNICAL FIELD

The present invention relates to a testing method of an electrochemicalgas sensor used for measuring the component concentration of a carbonmonoxide gas. In more detail, the present invention relates to a testingmethod for judging an operation condition of an electrochemical gassensor for use in a gas alarm unit which is ordinarily provided in aship or manhole, tunnel or home, and widely used for the prevention ofpoisoning accidents, caused by the blowout gas or the exhaust gas of aheater or car, the early detection of the fire, the prevention of firecaused by explosion, and the like.

BACKGROUND TECHNOLOGY

The electrochemical gas sensor is a sensor which introduces the gascomponent to be detected onto a working electrode having a catalyticaction through a membrane, and outputs the voltage or currentcorresponding to the gas concentration by oxidizing or reducing the gas,and because the sensor has a small size and light weight, and operatesunder the normal temperature and normal pressure, and is highly reliableand relatively low cost, it is widely used for the poisoning alarm unitor the industrial measuring unit, and the like.

Conventionally, a general structure of the widely and practically usedelectrochemical gas sensor is as shown in FIG. 1. Further, a generalelectric circuit which electrically drives such the electrochemical gassensor, and by which the output is obtained, is shown in FIG. 2.According to FIG. 2, the principle of operation of the electrochemicalgas sensor will be described.

The sensor has the structure in which a synthetic resin holder (9), andoxygen permeable film pressing member (6), membrane pressing member (14)are used, and the gas permeable membrane (12), working electrode (11),counter electrode (8), reference electrode (13), electrolyte holdingmember (10), and lead wires (1), (2) and (4) to make electricalconduction to each electrode are arranged, and the electrolyte (7) ishermetically sealed inside. The electrode is the catalyst whose maincomponent is the precious metals such as platinum or platinum black, andby which the gas having the reduction action such as carbon monoxide,hydrogen, or the like, or the gas having the oxidation action iseffectively oxidized or reduced on the working electrode (11).

The potential of the working electrode (11) is held at a suitable valuefor the oxidation and reduction response of the gas to the referenceelectrode (13) by the external circuit shown in FIG. 2. In this case,the current is not circulated to and from the reference electrode whichis the reference of the potential, and which only regulates thepotential of the working electrode and has no relation to the reaction.

Further, because the potential of the counter electrode is notregulated, the potential of the counter electrode is the naturalelectrode potential for the reaction corresponding to the reaction onthe working electrode. Accordingly, the oxidation and reduction reactionof the gas to be measured occurs only on the working electrode, and thereaction of the other side occurs only on the counter electrode.

When the gas to be measured is diffused from the outside in thepermeable membrane (12) and reaches the working electrode (11), theoxidation reaction shown in the relational expression (A) occurs. On theone hand, simultaneously, on the counter electrode (8) through theelectrolyte (7), the reduction reaction of the oxygen shown in therelational expression (B) occurs. The oxygen diffuses in the oxygenpermeable membrane (5) from the atmosphere in which the sensor is used,and is dissolved in the electrolyte (7), and diffused in the electrolyteand reaches the counter electrode (8).

(Working electrode reaction) CO+H₂O→CO₂+2H⁺+2e⁻  (A)

(Counter electrode reaction) 1/2O₂+2H⁺+2e⁻→H₂O  (B)

(Total reaction) CO+1/2O₂→CO₂  (C)

At this time, the current flows between the working electrode and thecounter electrode is shown by the relational expression (D), and isproportional to the concentration of the gas to be measured; therefore,by leading the current through the lead wire (4) connected to theworking electrode and the lead wire (2) connected to the counterelectrode to the outside, the concentration of the gas to be measuredcan be detected.

(the relationship of the reaction current and gas concentration)$\begin{matrix}{i = {\frac{F \times A \times D \times C}{\sigma} \times n}} & (D)\end{matrix}$

Where:

i: reaction current

F: Faraday constant

A: area of the diffusion surface

D: diffusion coefficient of the gas

C: concentration of the gas

σ: thickness of the diffusion layer

n: number of reaction electrons

(in the reaction of the sensor, F, A, D, σ, n are constant)

In the case of the reaction, concerning the water (H₂O) consumed on theworking electrode by the oxidation of the carbon monoxide gas, becausethe amount of the equivalent is generated by the reduction of the oxygen(O₂) in the outside air on the counter electrode, there is no chemicallyconsumed component.

However, in the practical use, there is a case in which the sensor isnot operated normally, by the extrinsic factors such as the agingdeterioration of members constituting the sensor or the contactcontinuity condition, or the stain of the membrane through which the gasdiffuses and penetrates.

Accordingly, when ordinarily, the poisoning alarm unit or the measuringdevice using such the electrochemical carbon monoxide gas sensor isused, the inspection or correction of the sensor output is necessarybefore using, and when the use is for a long period of time even in thecontinuous use, it is necessary that the measurement is periodicallystopped for the correction or replacement of the sensor so that theaccuracy or reliability is maintained. Conventionally, the correction ofthe sensor is conducted in such a manner that the maintenance man or theuser himself flows the correction gas including a predeterminedconcentration carbon monoxide into the sensor and the sensor outputgenerated at the time is measured. However, it is very troublesome toconduct such the correction operation periodically, and there is apossibility that the correction operator is exposed to the carbonmonoxide gas for correction.

Further, due to such difficulties, the periodical inspection may not beconducted, and thus, in the case where the concentration of the carbonmonoxide of the atmosphere is increased, and a possibility of poisoningoccurs, the sensor may not normally operate, and the alarm may not beprovided accordingly.

DISCLOSURE OF THE INVENTION

The present invention is described in the following (1) to (9).

(1) A testing method of an electrochemical gas sensor, in which: aworking electrode which electrochemically oxidizes or reduces the firstgas component to be detected, a counter electrode which actselectrochemical reduction reaction or oxidation reaction correspondingto an oxidized or reduced amount of the first gas component, and anelectrolyte are provided; and an sensor output which is a value of theoxidation current or reduction current of the first gas component, iscalculated and the concentration of the first gas component is detected,the testing method of an electrochemical gas sensor, which includes thesteps of that: in which the voltage in which the current flows in thereverse direction to the oxidation current or reduction current of thefirst gas component, is applied between the working electrode and thecounter electrode from the outside; and after the second gas componentis generated on the working electrode so as to be a predeterminedconcentration by the electrolysis of the electrolyte, the sensor outputwhich is a value of the oxidation current or reduction current on theworking electrode of the second gas component, is measured, and in whichthe second gas component shows a sensor at output practicallyproportional to the sensor output of the first gas component in theconcentration corresponding to the concentration of the first gascomponent.

(2) The testing method of an electrochemical gas sensor described in(1), in which the sensor is tested by using a correction value which isa ratio of the output of the measuring sensor in the predeterminedconcentration of the second gas component, and the sensor outputcalculated according to the known reference from the predeterminedconcentration of the second gas component.

(3) The testing method of an electrochemical gas sensor described in(1), in which the sensor is tested by using a correction value which isa ratio of the second gas component concentration calculated accordingto the known reference from the measuring sensor output, and thepredetermined concentration of the second gas component.

(4) The testing method of an electrochemical gas sensor described in(1), in which the first gas component is carbon monoxide.

(5) The testing method of an electrochemical gas sensor described in(4), in which the electrolyte is an aqueous solution, and the second gascomponent is hydrogen.

(6) The testing method of an electrochemical gas sensor, in which thetesting is correction, and/or deterioration judgement, and/or lifejudgement.

(7) An electrochemical gas sensor, in which a testing means according tothe testing method described in (6), is provided.

(8) An apparatus which is provided with an electrochemical gas sensor,and a testing means according to the testing method described in (6).

(9) A control apparatus of the electrochemical gas sensor which isprovided with a testing means according to the testing method describedin (4).

As described above, at the time of the correction of an electrochemicalcarbon monoxide gas sensor, the present invention judges thedeterioration of the sensor by means of temporarily operating theelectrode potential by the outside, and generating the gas having thesame action as at the time when the correction gas flows, on theelectrode, and then, returning the potential to the normal potential,and by the reaction of the sensor upon the generated and remained gas,and can correct the sensor, without practically using the correction gasincluding carbon monoxide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a structural section of an electrochemicalcarbon monoxide gas sensor.

FIG. 2 is a view showing an electric circuit for the drive and output ofthe electrochemical carbon monoxide gas sensor.

FIG. 3 is a view showing a result in which the reaction characteristicsof the electrochemical carbon monoxide gas sensor are practicallymeasured, in order to show the action and the effect of the presentinvention.

FIG. 4 is a view showing a result in which the reaction characteristicsof the electrochemical carbon monoxide gas sensor, whose membranesection is stained, are practically measured, in order to show theaction and the effect of the present invention.

FIG. 5 is a view showing a result in which the reaction characteristicsof the electrochemical carbon monoxide gas sensor, in which an amount ofthe catalyst of the electrode is decreased, are practically measured, inorder to show the action and the effect of the present invention.

FIG. 6 is a view showing a result in which the current-voltagecharacteristics of the electrochemical carbon monoxide gas sensor arepractically measured, in order to show the action and the effect of thepresent invention.

Incidentally, in the drawings, numeral 1 is a reference electrode leadwire, numeral 2 is a counter electrode lead wire, numeral 3 is anO-ring, numeral 4 is a working electrode lead wire, numeral 5 is anoxygen permeable membrane, numeral 6 is an oxygen permeable membranepressing member, numeral 7 is an electrolyte, numeral 8 is a counterelectrode, numeral 9 is a holder, numeral 10 is an electrolyte holdingmember, numeral 11 is a working electrode, numeral 12 is a gas permeablemembrane, numeral 13 is a reference electrode, and numeral 14 is amembrane pressing member.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described.

An electrochemical carbon monoxide gas sensor oxidizes carbon monoxideand reduces oxygen by using a catalytic electrode, and the current dueto the reaction is used as a detection means of the gas concentration,and the catalytic electrode is effective not only for the carbonmonoxide, but also for other reactive gases.

For example, in the case of a sensor in which platinum black, whosecatalytic action is very strong, is used for the electrode, also whenhydrogen is supplied onto the working electrode instead of carbonmonoxide, the following reaction occurs and the sensor current isgenerated.

(Working electrode reaction) H₂→2H⁺+2e⁻  (F)

(Counter electrode reaction) 1/2O₂+2H⁺+2e⁻→H₂O  (G)

(Total Reaction) H₂+1/2O₂→H₂O  (H)

Also in this case, because the principle of operation of the sensor isthe same as in the case of carbon monoxide gas, the sensor is notnormally operated, due to the external factors such as the agingdeterioration of members constituting the sensor or the electricalcontact continuity condition, or stains of the membrane through whichthe gas diffuses or penetrates, or the like.

Further, as widely known, when the constant voltage is applied between 2precious metal electrodes in the solution electrolyte, the electrolysisof water occurs by the following reaction formulas, and hydrogen isgenerated from one electrode (negative electrode ) and oxygen isgenerated from the other electrode (positive electrode).

(Negative electrode reaction) 2H⁺+2e⁻→H₂  (F)

(Positive electrode reaction) H₂O→1/2O₂+2H⁺+2e⁻  (G)

(Total reaction) H₂O→H₂+1/2O₂  (H)

Accordingly, when the constant voltage is applied from the outside sothat the working elect rode is operated as the negative electrode, andthe counter electrode is operated as the positive electrode, hydrogen isgenerated from the working electrode, and oxygen is generated from thecounter electrode. After that, when the potential of the workingelectrode and the counter electrode is returned to the operationpotential as the sensor, it reacts on the hydrogen remained in thevicinity of the working electrode, and the sensor current is generated.

Because this reaction on the hydrogen is the same as the reaction on thecarbon monoxide, when the difference from the reference value isextremely large by the comparison of the sensor current at that time tothe previously obtained reference value, it shows that the degree of thedeterioration of the carbon monoxide sensor is large, and when thedifference is small, it shows that the degree of the deterioration issmall.

Accordingly, whether the sensor is normally operated for the carbonmonoxide, can be greatly easily and simply tested and detected.

The reference sensor output means a sensor output when concretely, thecarbon monoxide gas sensor is used, and the electrolyte water issubjected to the electrolysis for a predetermined time, and hydrogen isgenerated and remained for a predetermined time, and it may be apreviously made value, or a value measured at the same hydrogengeneration time and remained time, before the deterioration judgementtime or the measurement at the time of correction.

Further, it may be compared, while periodically obtaining the sensoroutput as described above, with the relationship of the before andafter. On the one hand, the reference hydrogen concentration means thehydrogen concentration in which the sensor output is converted by thecalibration curve, and the like. In addition to that, in the comparison,at least 2 points of the reference value and the measuring value arenecessary. Therefore, it may be judged by using multi-points.

When water is electrolyzed, the concentration of hydrogen generated onthe working electrode is 100%, and is very thick as compared to theconcentration of hydrogen corresponding to 10 to 1,000 ppm which is theconcentration of carbon monoxide as an object of the normal measurement,however, when the time to electrolyze water is reduced to a short time,and the measurement is conducted after the passage of an appropriatetime, a large part of the hydrogen diffuses into the outside air, and anappropriate amount of hydrogen remains in the vicinity of the electrode,therefore, there is no problem. Further, although water in theelectrolyte is consumed by the electrolysis of water, when the time toelectrolyze water is reduced to a short time, because the consumedamount of the water is very small, there is no problem for the functionof the sensor.

Further, in the case where it is disadvantageous to the measurement ofthe concentration of carbon monoxide that interference of thesensitivity by hydrogen occurs, there are cases in which the hydrogen isselectively reacted and removed by using catalysis such as rutheniumwhich selectively reacts on the hydrogen, on the front stage of the gasintroducing portion of the sensor, or the hydrogen is selectivelyremoved by using the difference of the rate of absorption of hydrogenand carbon monoxide, by using the absorbent such as activated carbon,zeolite, or the like, in the same manner, on the front stage of the gasintroducing portion of the sensor, however, because the method of thepresent invention directly uses the reaction acted on the workingelectrode, the method is not influenced by the means arranged on thefront stage portion of the sensor.

EXAMPLES

As an example which preferably realizes the effect of the presentinvention, an electrochemical carbon monoxide sensor having thestructure in FIG. 1 is made on an experimental basis, and the effect isconfirmed.

The working electrode, counter electrode and reference electrode aremade by heating and press-fitting the kneaded material of watersuspension of water and ethylene tetra fluoride polymer (made by Mitsuiphloro-chemical Co. Trade name is 30-J) onto the stainless plate whichis made mesh-like, and on which platinum black is used as catalyst.

Platinum is used for each lead wire. For gas permeable membrane, 0.3 mmthick porous fluororesin (made by Sumitomo Denko Co., trade name:Phloro-pore FY-050), and for oxygen permeable membrane, 0.1 mm thickporous fluororesin film (made by Nitto Denko Co. trade name: NTF-1122)are used by being punched out to the predetermined shape.

For the electrolyte, sulfuric acid of 6 mol/L concentration is used. Thepotential of the working electrode and counter electrode is set by usingthe constant potential generator (made by Hokuto Denko Co. trade name:Potentiostat) as a unit which can perform the role of the operationalamplifier in FIG. 2, and by using the potential of the referenceelectrode as the reference, the potential of the working electrode isset, and the sensor output is measured.

In order to check that hydrogen gas is effective as the correction ordeterioration judgement gas, the reaction of the sensor on the carbonmonoxide and the reaction on the hydrogen are investigated. The resultof this is shown in FIG. 3.

In FIG. 3, the sensor output current to the various concentration of thecarbon monoxide and hydrogen, and the ratio of the output to the carbonmonoxide and the output to the hydrogen are shown, and thecharacteristics of the reaction of the sensor shows the same inclinationto both of them although there is a difference of outputs between them,and the ratio of the output is a constant value without depending on theconcentration.

Accordingly, in the normal measurement range, the sensor output by thecarbon monoxide has the relationship of 1 to 1 to the output by thehydrogen, and because, by the output value to either one gas, theconcentration of the other gas can be known, it is confirmed that thehydrogen gas is effective as the correction or/and deteriorationjudgement gas of the electrochemical carbon monoxide sensor.

Next, in order to investigate that hydrogen gas is effective as thecorrection or deterioration judgement gas, even when the sensor isabnormal, out of the normal measurement range, the sensor in which thefouling condition is reproduced such that water drops are intentionallyput on a portion of the gas permeable membrane, and the sensor in whichthe condition that the catalyst capability is deteriorated, isreproduced by decreasing the amount of the catalyst which ispress-fitted onto the working electrode, are respectively made on anexperimental basis, and their characteristics are investigated.

The measurement result of the output characteristics of the sensor whosegas permeable membrane is fouled, is shown in FIG. 4, and themeasurement result of the output characteristics of the sensor whosecatalysis amount is decreased, is shown FIG. 5. In any case of FIG. 4and FIG. 5, in the same manner as in the result in FIG. 3, the ratio ofthe outputs is constant without depending on the concentration.

From the result of the experiments shown in FIG. 3, FIG. 4 and FIG. 5,not only in the normal measurement range, but also in the abnormal case,the sensor output by the carbon monoxide has the relationship of 1 to 1to the output by the hydrogen, and because, by the output value toeither one gas, the concentration of the other gas can be known, thehydrogen gas is effective as the correction or/and deteriorationjudgement gas of the electrochemical carbon monoxide sensor.

In order to verify the condition of generation of hydrogen by theelectrolysis of water in this sensor, the potential of the workingelectrode is scanned with respect to the reference electrode, and thechange of the current value at that time is checked. The result of thisis shown in FIG. 6.

In FIG. 6, the axis of ordinate shows the potential of the workingelectrode using the reference electrode as the reference (0 V). Further,the reaction of the other side of the reaction of the working electrodeoccurs on the counter electrode. In this case, in the positive side ofthe axis of ordinate, the working electrode acts the positive electrode,that is, the side of generation of oxygen, and in the negative side, theworking electrode acts as the negative electrode, that is, the side ofgeneration of hydrogen. The theoretical decomposition voltage of wateris, as well known, 1.23 V.

In the practical reaction, the over-voltage is generated according tothe nature of the electrode, and generation voltage of hydrogen andoxygen is higher than the theoretical voltage, and in the case of thesensor, from FIG. 6, it is found that, because of rapid increase of thecurrent value, the generation of oxygen occurs from the vicinity inwhich the voltage difference from the reference electrode exceeds 1200mV, and the generation of hydrogen occurs from the vicinity in which thevoltage difference from the reference electrode exceeds −400 mV. Becausethe sum of absolute values of the both is the voltage difference atwhich the generation of hydrogen and oxygen by the electrolysis of wateroccurs between the working electrode and the counter electrode, it isfound that, in the case of the sensor, the generation of hydrogen andoxygen by the electrolysis of water occurs at about 1600 mV.

Accordingly, when the potential of the working electrode to thepotential of the reference electrode of the sensor is not more than −600mV, the hydrogen can be generated on the working electrode.

From these results, it is confirmed by conducting the following teststhat, without using the correction gas including the carbon monoxidecomponents, the correction or/and deterioration judgement of the sensorcan be electrically conducted from the outside.

From the normal measurement condition in which the potential of theworking electrode whose reference is the reference electrode, is keptbetween about 0 to −300 mV, the potential is lowered to −600 mV for apredetermined time, and hydrogen is generated, and after a predeterminedtime (standing time), the condition is returned again to the measurementcondition, and the sensor output value at that time is converted to theconcentration of carbon monoxide gas (hydrogen gas concentration)according to the characteristics shown in FIG. 3. The result is shown inthe following Table 1.

TABLE 1 concentration equivalent to hydrogen measurement carbongeneration waiting time sensor output monoxide time (sec) (min) (μA)(ppm) 1.0 1 23.0 958 1.0 2 10.2 425 1.0 3 3.9 162 1.0 5 0.8  33 2.0 320.5 854 2.0 5 6.4 267 0.5 1 10.8 450 0.5 3 0.3  12

From Table 1, by controlling the hydrogen generation time and standingtime, it is found that the sensor response in the wide concentrationequivalent to carbon monoxide (concentration of hydrogen) can beobtained. Accordingly, when it is desired to confirm the condition ofthe sensor in the vicinity of the necessary gas concentration, bysetting an arbitrary hydrogen generation time and an arbitrary standingtime, the deterioration condition, or the like, of the sensor in thevicinity of the necessary concentration can be grasped. Accordingly,when the hydrogen generation time and the measurement waiting time areappropriately selected, the correction corresponding to various carbonmonoxide concentration can be conducted.

In order to confirm this, a carbon monoxide gas sensor is prepared, andwhen the hydrogen generation time is set to 1 sec., and the standingtime is set to 2 min., the concentration equivalent to carbon monoxideis 425 ppm, as shown in Table 1, and this is defined as the referencevalue. Then, the sensor is deteriorated, and the concentrationequivalent to the carbon monoxide, which is converted from the sensoroutput at the same generation time and standing time of the sensor, is200 ppm. Naturally, 425 ppm or the value near the value should beobtained, however, it is shown that, because the responsibility islowered by the deterioration, the value does not coincide with the valueof 425 ppm.

The correction value which is a ratio of the two, is 200/425=0.4706, andas described above, because the concentration of the carbon monoxide andthe concentration of hydrogen have the relationship of 1 to 1, when theconcentration of carbon monoxide is measured by this deteriorated sensorand 180 ppm is obtained, the corrected concentration of carbon monoxideis 180/0.4706=382.5 ppm.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, only byperiodically applying the voltage from the outside, the correction anddeterioration judgement of the electrochemical carbon monoxide can becarried out, and it is not necessary that the correction gas includingcarbon monoxide is made to practically flow to the sensor and thecorrection operation is carried out, and without being accompanied by apossibility that the correction service man is exposed to the carbonmonoxide gas for correction, the correction operation is periodicallycarried out easily and simply.

Further, the periodical sensor correction or testing can be carried outby the electric signals from the outside, and when the concentration ofthe carbon monoxide in the circumstance is increased practically, and apossibility of poisoning is generated, a possibility that the sensor isnot normally operated and alarm is not given, can be greatly decreased.

Accordingly, the present invention can greatly attribute to theindustry.

What is claimed is:
 1. A method for testing an electrochemical gassensor, wherein the electrochemical gas sensor includes a workingelectrode which electrochemically oxidizes or reduces a first gascomponent to be detected, a counter electrode which causes anelectrochemical reduction reaction or oxidation reaction correspondingto an oxidized or reduced amount of the first gas component, and anelectrolyte, and wherein a sensor output, which is a value of anoxidation current or reduction current of the first gas component, iscalculated and a concentration of the first gas component is detected,comprising the steps of: applying a voltage in which the current flowsin the reverse direction to the oxidation current or reduction currentof the first gas component, between the working electrode and thecounter electrode from an outside of the electrochemical gas sensor, sothat the working electrode operates as a negative electrode and thecounter electrode operates as a positive electrode; and after a secondgas component is generated on the working electrode so as to be apredetermined concentration by the electrolysis of the electrolyte,measuring the sensor output which is a value of the oxidation current orreduction current on the working electrode of the second gas component,wherein a normal operation of the electrochemical gas sensor isdetermined if the second gas component has a sensor output substantiallyproportional to the sensor output of the first gas component in aconcentration corresponding to the concentration of the first gascomponent.
 2. The testing method of an electrochemical gas sensordescribed in claim 1, wherein the sensor is tested by using a correctionvalue which is a ratio of the output of the measuring sensor in thepredetermined concentration of the second gas component, and the sensoroutput calculated according to a reference value from the predeterminedconcentration of the second gas component.
 3. The testing method of anelectrochemical gas sensor described in claim 1, wherein the sensor istested by using a correction value which is a ratio of the second gascomponent concentration calculated according to a reference value fromthe measuring sensor output, and the predetermined concentration of thesecond gas component.
 4. The testing method of an electrochemical gassensor described in claim 1, wherein the first gas component is carbonmonoxide.
 5. The testing method of an electrochemical gas sensordescribed in claim 4, wherein the electrolyte is an aqueous solution,and the second gas component is hydrogen.
 6. A control apparatus of theelectrochemical gas sensor wherein a testing means according to thetesting method described in claim 4, is provided.
 7. The testing methodof an electrochemical gas sensor described in claim 1, wherein thetesting is correction, and/or deterioration judgement, and/or lifejudgement.
 8. An electrochemical gas sensor, wherein a testing meansaccording to the testing method described in claim 7, is provided.
 9. Anapparatus wherein an electrochemical gas sensor, and a testing meansaccording to the testing method described in claim 7, are provided.